1---2id: H163title: Statistically detectable input–output correlations vanish after a small number of steps4axis: C5kind: sha2566statement: With N = 20 000 samples, the number of (input bit, output bit) pairs with |corr| > 4/√N is large for s ≤ 4 and7 zero for s ≥ s** (to be measured), identical to the random-oracle control; output-byte chi-square tests are uniform beyond8 s**.9motivation: C1/C3.10assumptions: Single-block random messages.11expected_contribution: Bias figure.12related_work:13- nist2015fips18014possible_counterexamples: Residual correlations at 64 steps.15verification_strategy: experiments/reduced_round_sha256/bias_test.py16computational_budget: minutes17status: running18classification: pending19evidence: []20verdict: pending21---2223# H16 — Statistically detectable input–output correlations vanish after a small number of steps2425With N = 20 000 samples, the number of (input bit, output bit) pairs with |corr| > 4/√N is large for s ≤ 4 and zero for s ≥ s** (to be measured), identical to the random-oracle control; output-byte chi-square tests are uniform beyond s**.26